The Myeloproliferative Disorders (MPD) Research Consortium focuses on the Philadelphia (Ph) chromosome negative MPD including Polycythemia Vera (PV), and Idiopathic Myelofibrosis (IM) and has the following goals: 1) Establish a multi-institutional international research group entitled the "MPD Research Consortium" which will coordinate and facilitate basic and clinical research dealing with the cellular and genetic basis of the Ph negative MPD. 2) Establish a multi-institutional MPD Clinical Consortium to enable uniform, high volume sample collection, storage and distribution. 3) Perform rationally designed clinical trials in patients with Ph negative MPD at multiple institutions. 4) Maintain an interactive website for MPD Consortium investigators, a sophisticated international tissue bank and an on-line database that will allow for integration of basic and clinical research. This unique interactive relationship between talented basic researchers and clinical scientists will permit the MPD Research Consortium to develop novel clinical treatment programs for Ph negative MPD and to identify specific biomarkers that will be useful as indicators of therapeutic response and/or risk reduction. This program has six major projects: Project 1: Genetic Basis of Polycythemia Vera, Principal Investigator: Josef T. Prchal;Project 2: Mechanisms and Effects of NF-E2 and PRV-1 Overexpression in PV: Role of Jak2V617F, Principal Investigator: Heike L Pahl;Project 3: Animal Models of Polycythemia Vera, Principal Investigator: Jerry Spivak;Project 4: Mouse Models of Myelofibrosis, Principal Investigator: Anna Rita Migliaccio;Project 5: Abnormal Stem Cell Trafficking in Myelofibrosis, Principal Investigator: Ronald Hoffman;Project 6: MPD Clinical Consortium which will pursue clinical trials in PV and IM, Principal Investigator: Lewis Silverman and Co-Principal Investigator: Tiziano Barbui. The six projects will be supported by one core: Tissue Bank, Principal Investigator: Rona Weinberg. These unique interactions between clinical and laboratory investigators which are interwoven within the MPD Research Consortium will ultimately result in improved understanding of the pathobiology of the Ph negative MPD as well improved strategies that will assist in the diagnosis and treatment of these disorders.